This project is an extension of a research program investigating the spinal mechanisms mediating sexual function. It has long been known that fully developed sexual reflexes are more easily elicited in spinalized animals compared to intact or decerebrated animals. This has led many researchers to postulate that spinal sexual circuits are under descending inhibitory control from the brainstem. This proposal, using anatomical and physiological techniques, seeks to answer the question: What are the sources of descending control of spinal sexual reflexes? This study will exploit a preparation we have developed, in which fully developed sexual responses (the coitus reflex) can be elicited in anesthetized rats. The coitus reflex can only be seen in this preparation following spinalization, implying a descending inhibition of this system. The first set of experiments will determine the source of this inhibition by means of brainstem sites which provide descending control of sexual reflexes. The next set of experiments will use retrograde and anterograde tract tracing techniques to determine the projections of these brainstem sites. A primary goal of these studies is to determine if the descending inhibition and stimulation of the identified brainstem sites. These studies will determine if descending control is mediated by graded inhibition of efferent activity, gating of segmental sensory input, or by modulating the spatial and temporal aspects of the spinal pattern generator which produces sexual responses.